CN107046677B

CN107046677B - Techniques for measuring location of a UE

Info

Publication number: CN107046677B
Application number: CN201710140793.0A
Authority: CN
Inventors: 林秀焕; 李尚旭; 郑万永; 李大远; 梁润吾
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2010-12-14
Filing date: 2011-12-08
Publication date: 2020-10-09
Anticipated expiration: 2031-12-08
Also published as: US9084127B2; WO2012081861A2; US20130260793A1; WO2012081861A3; CN103329604B; EP2652995A4; US20150365836A1; JP6185520B2; EP2652995B1; US9961680B2; KR101527041B1; EP2652995A2; US9374728B2; KR20130115321A; US20160286552A1; CN103329604A; JP2014504369A; CN107046677A; JP2016001188A; JP5796085B2

Abstract

The present invention relates to a technique for measuring the position of a UE. The present invention provides a method for measuring a position. The method comprises the following steps: receiving, by a User Equipment (UE) and from a serving cell, information on a bandwidth allocated for a Positioning Reference Signal (PRS); receiving, by a User Equipment (UE) and from at least one or more neighboring cells, information on a bandwidth allocated for PRSs; determining whether there is a difference between the bandwidths; and measuring, by the UE and based on a result of the determining, a timing difference between PRSs transmitted from the serving cell and the at least one or more neighbor cells.

Description

Techniques for measuring location of a UE

The present application is a divisional application of the international application No. 201180060291.8(PCT/KR2011/009493) filed on 6/14/2013, 2011, 12/8, entitled "technique for measuring location of UE" patent application.

Technical Field

This description relates to position measurement.

Background

Second generation (2G) mobile communication refers to transmission and reception of voice to digital, and is represented by Code Division Multiple Access (CDMA), global system for mobile communication (GSM), and the like. General Packet Radio Service (GPRS) has evolved from GSM. GPRS is a technology for providing a packet-switched data service based on a GSP system.

Third generation (3G) mobile communication refers to transmission and reception of images and data as well as voice (audio). The third generation partnership project (3GPP) has developed mobile communication systems, i.e., international mobile telecommunications (IMT-2000), and adaptive wideband cdma (wcdma) as Radio Access Technologies (RATs). IMT-200 and RATs, such as WCDMA, are known as Universal Mobile Telecommunications System (UMTS) in Europe. Here, UTRAN is an abbreviation of UMTS terrestrial radio access network.

Meanwhile, third generation mobile communication is evolving into fourth generation (4G) mobile communication.

As 4G mobile communication technologies, a long term evolution network (LTE) which is being standardized in 3GPP and IEEE 802.16 which is being standardized in IEEE implementation have been introduced. LTE uses the term "evolved UTRAN (E-UTRAN)".

The 4G mobile communication technology has adopted Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA). OFDM uses multiple orthogonal subcarriers. OFDM uses the property of orthogonality between the Inverse Fast Fourier Transform (IFFT) and the Fast Fourier Transform (FFT). The transmitter performs IFFT on the data and transmits the data. The receiver performs FFT on the received signal to restore the original data. The transmitter uses IFFT for concatenating the multiple subcarriers, and the receiver uses corresponding FFT to divide the multiple subcarriers.

Meanwhile, the 3G or 4G mobile communication system has a functional part for calculating a location (or position) of a terminal to provide a location service, which provides the position of the terminal.

Currently, there are several methods for calculating the position of a terminal, including a cell ID method for transmitting an ID of a cell to which a mobile terminal belongs, a method for calculating the position of a terminal via triangulation by measuring time taken for a radio signal to reach each base station from the terminal, and a method using a satellite.

In the cell ID (i.e., cell coverage) based approach, the UE's location is estimated with knowledge of its serving base station (i.e., serving node B). The information about the serving node B and the cell may be obtained during a paging procedure, a positioning area update procedure, a cell update procedure, a URA update procedure, or a routing area update procedure.

The cell coverage based positioning information may be indicated as a cell identity, a serving area identity of the used cell, or as geographical coordinates of a positioning related to the serving cell. The positioning information includes a QoS estimate (e.g., as to accuracy of implementation) and, if available, a positioning method (or list of methods) is used to obtain the position estimate.

When geographical coordinates are used as positioning information, the estimated location of the UE may be a fixed geographical location within the serving cell (e.g., the location of the serving node B), the geographical location center of the coverage area of the serving cell, or some other fixed location within the coverage area of the cell. The geographical position may also be obtained by combining information about the cell-specific fixed geographical position with other available information, such as the signal RTT in FDD or Rx timing (timing) offset measurement and knowledge of the UE timing advance in TDD.

Meanwhile, for the method using the satellite, the UE must be equipped with a radio receiver capable of receiving the GNSS signal. In practice, examples of GNSS include GPS (global positioning system) and Galileo (Galileo). In this concept, different GNSS (e.g. GPS, galileo) may be used separately or in combination to perform positioning of the UE.

Furthermore, methods using triangulation techniques can be divided into two types of techniques. One is the U-TDOA location method and the other is the OTDOA-IPDL (network adjustable idle period observed time difference of arrival in downlink) method.

First, the U-TDOA location method is based on network measurements of time of arrival (TOA) of known signals sent from UEs and received at four or more LMUs. This approach requires LMUs near the geographical location of the located UE to accurately measure the TOA of the pulse. Since the geographical coordinates of the measurement units are known, the UE position can be calculated via hyperbolic trilateration. This approach will work with existing UEs without any improvement. In most cases, a UE deep inside the cell coverage radius does not need to receive signals from other cells. Only when the UE moves to the edge of cell coverage, it needs to listen to signals from other cells and may switch to other cells. This is in contrast to the UE location acquisition procedure, where the UE may listen to more than 1 cell regardless of the UE geographical location needs.

Second, the OTDOA-IPDL (network adjustable idle period observed time difference of arrival in downlink) method involves measurements by UEs of frame timing (e.g., system frame number to system frame number observed time difference).

FIG. 1 shows a schematic view of a

Fig. 1 illustrates an exemplary OTDOA method.

Referring to fig. 1, the OTDOA-IPDL (network adjustable idle period observed time difference of arrival in downlink) method involves measurements by UEs of frame timing (e.g., system frame number to system frame number observed time difference). These measurements are used in the network and calculate the location of the UE. The simplest case of OTDOA-IPDL is no idle period. In this case, the method may be referred to as simple OTDOA. The node B may provide idle periods in the downlink to potentially improve the audibility of neighboring node bs. The support of these idle periods is optional in the UE.

Thus, in the OTDOA technique, the UE must measure a timing difference (timing difference). However, if bandwidths allocated by each cell are different from each other, the UE suffers from poor measurement timing.

Disclosure of Invention

Technical scheme

Accordingly, one aspect of the present description is to address the above-mentioned disadvantages. That is, an aspect of the present specification is to provide a solution for solving a problem that bandwidths allocated by each cell are different from each other.

In more detail, the solution may allow the UE to measure timing differences in the case where bandwidths allocated by each cell are different from each other. Furthermore, the solution may allow each cell to synchronize its bandwidth with other cells.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for measuring a position. The method comprises the following steps: receiving, by a User Equipment (UE) and from a serving cell, information on a bandwidth allocated for a Positioning Reference Signal (PRS); receiving, by a User Equipment (UE) and from at least one or more neighboring cells, information on a bandwidth allocated for PRSs; determining whether there is a difference between the bandwidths; and measuring, by the UE and based on a result of the determining, a timing difference between PRSs transmitted from the serving cell and the at least one or more neighbor cells.

The bandwidth may have an intra-frequency based relationship.

The measuring may include: selecting a largest bandwidth among the bandwidths if there is a difference; setting at least one parameter for measuring a timing difference between PRSs based on the maximum bandwidth; and measuring a timing difference between the PRSs according to the parameter. Here, the parameter includes at least one of: a first parameter related to accuracy relative to the measurement; and a second parameter related to the number of subframes available for measurement.

Alternatively, the measuring may include: if there is a difference, a request message for requesting a gap between the PRS of the first base station and the PRS of the neighboring base station is transmitted.

During the gap, the UE does not receive any data from the first base station.

Alternatively, the measuring may include: selecting a smallest bandwidth among the bandwidths if there is a difference; setting at least one parameter for measuring a timing difference between PRSs based on the minimum bandwidth; and measuring a timing difference between the PRSs according to the parameter.

Preferably, in the selecting step, if the first base station is not the reference cell, the smallest bandwidth may be selected.

The measuring may further comprise: information on the set parameters is transmitted to the first base station.

To achieve these aspects of the present specification, a method for measuring a position performed by a first base station is provided. The method can comprise the following steps: receiving, by a first base station and from at least one or more neighboring base stations, information on bandwidths allocated for positioning reference signals of the neighboring base stations; determining whether there is a difference between a bandwidth of a neighboring base station and a bandwidth of a PRS allocated for a first base station; and if there is a difference, performing a process so that the bandwidths are equal to each other.

The process may include transmitting a control signal for requesting a neighboring base station to adjust a bandwidth to be equal to a bandwidth of the first base station.

Alternatively, the process may include adjusting the bandwidth of the first base station to equal the bandwidth of the neighboring base station.

To implement the aspects of the present specification, a user equipment is provided. The UE may include: a transceiver configured to receive information on a bandwidth allocated for a Positioning Reference Signal (PRS) from a serving cell and information on a bandwidth allocated for a PRS from at least one or more neighbor cells; and a controller configured to determine whether there is a difference between bandwidths, and control the transceiver to measure a timing difference between PRSs transmitted from the serving cell and at least one or more neighbor cells based on a result of the determination.

To implement the aspects of the present specification, a base station is provided. The base station may include a transceiver configured to receive information on bandwidths of positioning reference signals allocated for neighbor base stations from at least one or more neighbor base stations; and a controller cooperating with the transceiver and configured to determine whether there is a difference between a bandwidth of the neighboring base station and a bandwidth of the PRS allocated for the first base station, and if there is a difference, the controller performs a process such that the bandwidths are equal to each other.

Drawings

FIG. 1 illustrates an exemplary OTDOA method;

FIG. 2 illustrates one example scenario for detecting positioning RSs in an OTDOA method;

figure 3 illustrates one example of propagation delay from cells a and B;

figure 4 illustrates one example of a relative transmission time difference between two cells;

fig. 5 illustrates one example of necessity of 3 subframes to prevent interference from a serving cell.

FIG. 6 illustrates an exemplary location transfer process;

figure 7 illustrates the RSTD reporting time requirement in FDD mode;

fig. 8 illustrates one example of a situation where the bandwidth allocated by the serving cell is different from the bandwidth allocated by at least one or more neighboring cells;

fig. 9 illustrates a first embodiment of the present invention, in which the longest BW in the serving cell and the neighbor cells is considered to measure PRS;

fig. 10 illustrates a second embodiment of the invention, in which the bandwidth of a first cell is adjusted to be equal to the bandwidth of another cell;

FIG. 11 illustrates a third embodiment of the present invention;

fig. 12 illustrates an example of a measurement gap according to a third embodiment of the present invention;

fig. 13 illustrates a case where the serving cell is not defined as the reference cell and the bandwidth allocated by the serving cell is greater than the bandwidth allocated by the target cell;

fig. 14 illustrates a problem and a solution that arise in a situation where the serving cell is not defined as a reference cell and the bandwidth allocated by the serving cell is smaller than the bandwidth allocated by the target cell, according to a fourth embodiment; and

fig. 15 is a block diagram illustrating the configuration of the UE 100 and the base station 200 according to the present invention.

Detailed Description

This description applies, but is not limited to, measurement techniques for the location of user equipment. This description may apply to any communication system and method to which the technical scope of this description may be applied.

Technical terms used in the present specification are only used to illustrate specific embodiments, and it should be understood that they are not intended to limit the present disclosure. To the extent that they are not defined differently, all terms including technical or scientific terms used herein may have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs, and should not be interpreted in an overly broad or overly restrictive sense. Further, if a technical term used in the description of the present disclosure is an erroneous term, which fails to clearly express the idea of the present disclosure, it will be replaced with a technical term that can be correctly understood by those skilled in the art. Furthermore, conventional terms used in the description of the present disclosure will be interpreted according to the definitions in the dictionary or according to the preceding or following context thereof, and should not be interpreted to have an excessively restrictive meaning.

To the extent that it is expressly stated that it is different from the context, singular references can include plural references. The terms "comprising" or "having" as used herein should be understood that they are intended to indicate the presence of several elements or steps disclosed in the present specification, and they may also be understood to not include parts of the elements or steps, or may further include additional elements or steps.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure.

It will be understood that when an element is referred to as being "connected to" another element, it can be directly connected to the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly connected to" another element, there are no intervening elements present.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings, where the same or corresponding parts bear the same reference numerals regardless of the figure number, and redundant explanations are omitted. In describing the present invention, if a detailed explanation for a related known function or construction is considered to unnecessarily divert the gist of the present invention, such explanation has been omitted but will be understood by those skilled in the art. The accompanying drawings are provided to help easily understand the technical idea of the present invention, and it should be understood that the idea of the present invention is not limited by the accompanying drawings. The inventive concept is to be construed as being extended to any variations, equivalents, and alternatives except as may be seen in the accompanying drawings.

The term "terminal" is used herein, but a terminal may be replaced with other terms, such as User Equipment (UE), Mobile Equipment (ME), Mobile Station (MS), and the like. Further, the terminal may be of the type of a portable device, such as a cellular phone, PDA, smart phone, notebook, etc., or of the type of a stationary device, such as a PC, car-mounted device, etc.

Prior to describing the present invention with reference to the accompanying drawings, the technology explained in the specification of the present invention will be briefly described to assist understanding of the present invention.

An example embodiment of the present invention uses OTDOA techniques based on the 3GPP standard, in which a User Equipment (UE) receives Positioning Reference Signals (PRS) transmitted from multiple cells using the same E-UTRA absolute radio frequency channel number (EARFCN), and the UE measures Reference Signal Time Difference (RSTD). Accordingly, an exemplary embodiment of the present invention provides a technique for improving the measurement accuracy of RSTD.

The requirement for accuracy is defined in 3GPP standard document TS 36.133. In more detail, this document describes that the measurement satisfies the accuracy in terms of transmission bandwidth allocated for PRS by the neighboring cell. Here, the bandwidth allocated for the channel of the PRS is independent of the bandwidth in which the PRS itself is transmitted. Accordingly, after acquiring information on a bandwidth allocated by the target neighbor cell for the PRS channel, the UE receives the PRS during the channel, calculates an RSTD between the PRS from the serving cell and the PRS from the target neighbor cell, and then transmits information of the calculated RSTD.

However, the standard document theoretically assumes that the serving cell and the neighbor cell allocate the same bandwidth for PRS. However, the bandwidth allocated by the serving cell may be different from the bandwidth allocated by the neighboring cells. In this case, since the UE considers only the bandwidth of the serving cell and does not consider the bandwidths of the neighboring cells transmitted using the same EARFCN, the accuracy is degraded and it is difficult to satisfy the requirement.

Accordingly, an exemplary embodiment of the present invention provides a solution that satisfies measurement accuracy even when bandwidths are different from each other.

Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIGS. 2 and 3

FIG. 2 illustrates one example scenario for detecting positioning RSs in an OTDOA approach. Also, fig. 3 illustrates one example of propagation delays from cells a and B.

Given that when a UE is connected to a serving cell, the UE attempts to receive certain signals from the target cell, there may be two possible scenarios.

Referring to fig. 2(a), the first case is that the path loss of a signal from cell a, which is the serving (anchor) cell, is smaller than the path loss of a signal from cell B, which is the target cell.

Referring to fig. 2(B), the second case is that the path loss of the signal from cell a is similar to the path loss of the signal from cell B.

In the second case, the received signals from both cells are being received at the UE with similar amplitudes, and if there is sufficient energy for reception of the measured signal from cell B, the UE can detect the signal and make the required measurements.

In the first case, the signal received from cell B arrives at the UE less than the signal received from cell a. In the UE, a signal amplification chain called Automatic Gain Control (AGC) will amplify the received total signal to fit (fit) the dynamic range of the analog-to-digital converter (ADC). If the received signal from cell a is greater than the signal from cell B, the total signal received will in fact be similar to the signal from cell a. Since the AGC only takes into account the total received signal when adjusting the amplifier gain, it is possible that the received signal from cell B is lost within the quantization error in the ADC. Therefore, in the first scenario, it is likely that the UE cannot detect the signal sequence from cell B, no matter how well the measurement signal sequence is designed.

To overcome possible scenarios such as the first mentioned scenario, the serving cell may configure an idle period, or a no signal transmission duration. This will effectively remove (kill) the signal from cell a and allow the AGC to adapt to the signal source from cell B, allowing enough ADCs for the received signal from cell B.

There are signal propagation delays involved when a signal is being transmitted through space (wireless propagation). For example, even if two signals are transmitted at the same instant of time depending on the location of signal reception, signals from two different transmission points may be received at different times. This is depicted as an example in fig. 3, where the UE is located far away from cell B compared to cell a.

Thus, signals from different cells may be received at different timings, regardless of whether the deployed cells are synchronized. For a system targeted at a maximum cell radius of 100km, the maximum transmission delay that can occur from the UE side would be approximately 100[ km ]/300000[ km/s ] s 0.334ms (microseconds). For synchronously deployed cells, the maximum signal deviation will be ± 0.334ms at the receiver side. For asynchronously deployed cells, the transmission signals at the eNB may already be out of sync. From a subframe perspective, the maximum deviation between two cells is ± 0.5ms (or half a subframe). This is because if the subframe timing difference between 2 cells with respect to two different reference subframes is greater than 0.5ms, the relative time difference is always less than or equal to ± 0.5ms, compared to the reference subframe can be redefined. Of course, this assumes that the subframe length is equal to 1ms, and all transmissions and measurements are made on a subframe-by-subframe basis.

FIGS. 4 and 5

Fig. 4 illustrates one example of a relative transmission time difference between two cells. Fig. 5 illustrates one example of necessity of 3 subframes to prevent interference from a serving cell.

Fig. 4(a) shows that the relative transmission time difference between two cells is 0 ms. Fig. 4(b) shows that the relative transmission time difference between the two cells is 0.5 ms. Fig. 4(b) shows that the relative transmission time difference between the two cells is 0.75ms, but from a different perspective this will result in a negative 0.25ms time difference.

For any given serving cell receiving a signal from a given target cell, a maximum of 3 subframes would need to be idle in order to receive a signal from a certain target cell without any interference from the serving cell.

Therefore, it may be necessary to configure consecutive 1, 2, or 3 idle subframes according to the measurement signal transmission timing of the target cell and the idle subframe timing of the serving cell.

Therefore, we can configure the network to have consecutive 1, 2 (or 3) idle subframes in the system according to the timing relationship between the serving cell and the measurement target cell. It is possible for the UE to report the measurement signal delay relative to the start of the first idle subframe of the serving cell. This would allow the eNB to calculate the relative delay of the measurement signal in a systematic way and limit the signal delay measurement to be within a maximum of 3 ms.

In order for the UE to make measurements without having to read the subframe boundary or radio frame boundary of the target cell, the serving cell may inform the UE of the target cell ID and the approximate measurement subframe timing given in terms of the serving cell's subframe number and system frame number. In addition, the serving cell may inform the UE of the measurement signal bandwidth and the frequency location of the measurement signal of the target cell. This would allow the UE to blindly detect the measurement signal without any target cell search and target cell synchronization procedure.

The information needed for measurements from the target cell may be broadcast by the serving cell. This includes the actual target cell ID. This is possible because the network already knows geographically the exact location of the eNB. This enables the serving cell to know the closest cells around it and also allows for the elimination of cells that are not conducive to delay measurement enhancement, such as cells with Tx antennas that are co-located with the serving cell (i.e., 3 sectors within the eNB).

FIG. 6

Fig. 6 illustrates an exemplary location transfer process.

Referring to fig. 6, a location information transfer process is shown.

First, the server sends a request location information message to the target to request location information indicating the type of location information needed and potentially associated with QoS.

The target sends a provide location information message to the server to convey the location information. Unless the server explicitly allows additional location information, the transmitted location information will match, or be a subset of, the location information requested in step 1. This message may carry an end transaction indication (end transaction indication).

The target sends an additional provide location information message to the server to convey the location information. Unless the server explicitly allows additional location information, the transmitted location information will match, or be a subset of, the location information requested in step 1. The last message carries an end transaction indication.

Meanwhile, the OTDOA neighbor cell information list may be sent by the network in order to facilitate measurement of PRS of other cells.

The IE OTDOA neighbor cell information list is used by the location server to provide neighbor cell information for OTDOA assistance data. The OTDOA neighbor cell information list is classified according to the best measurement geometry (geometry) estimated at the prior location of the target device. That is, the target device desires to provide measurements in increasing neighbor cell list order (to the extent this information may be available to the target device).

Table 1 shows the conditional presence of the neighbor cell information element in asn.1.

TABLE 1

[ Table 1]

In addition, table 2 shows OTDOA neighbor cell information list field description.

TABLE 2

[ Table 2]

Meanwhile, the configuration of the positioning rs (prs) will be explained below.

The cell-specific subframe configuration period T is listed in table 3 below_PRSAnd a cell-specific subframe offset Δ for transmission of a positioning reference signal_PRS. PRS configuration index I_PRSConfigured by higher layers. Positioning Reference Signals (PRSs) are transmitted only in configured DL subframes. PRSs are not transmitted in a specific subframe. In N_PRSSending PRSs in consecutive downlink subframes, where N_PRSConfigured by higher layers.

For N_PRSLocation reference signal instance of a first subframe of a downlink subframe satisfies

Table 3 shows a subframe configuration of PRS.

TABLE 3

[ Table 3]

PRS period T_PRS(subframe)

\|

[1280]
	[ reserved]

Meanwhile, the measurement of the positioning RS will be explained below.

When the physical layer cell identity of the neighbor cell is provided with the OTDOA assistance data, the UE can be at T_RSTDThe intra-frequency RSTD specified in 3GPP TS 36.214 is detected and measured on the same carrier frequency f1 for at least n-16 cells, including reference cells, within ms, as given below:

T_RSTD＝T_RSTD·(M-1)+Δms,

here T_RSTDIs a total time, T, for detecting and measuring at least n cells_PRSIs a cell-specific positioning subframe configuration period as defined in 3GPP TS 36.211, M is the number of PRS positioning occasions (occase) as defined in the following table, where each PRS positioning occasion comprises N as defined in 3GPP TS 36.211_PRS(1≤N_PRS≦ 6) consecutive downlink positioning subframes, and

ms is a measurement time for a single PRS positioning occasion, which includes a sampling time and a processing time.

Table 4 shows the results at T_RSTDA number of PRS positioning occasions within.

TABLE 4

[ Table 4]

Positioning subframe configuration period T_PRS
	160ms
>160ms

The UE physical layer is able to report the RSTD for the reference cell and provide all neighbor cells i:

for all the frequency bands of the cells for reference,

for all bands for neighbor cell i

And

conditions applicable to at least

All of the subframes of the PRS positioning occasions,

for bands 1, 4, 6, 10, 11, 18, 19, 21, PRP l,2| dBm ≧ 127dBm for band 9, PRP l,2| dBm ≧ 126dBm

For bands 2, 5, 7, PRP l,2| dBm ≧ 125dBm

For bands 3, 8, 12, 13, 14, 17, 20, PRP l,2| dBm ≧ 124 dBm.

Is defined as the ratio of the average received energy per PRS RE during the useful part of the symbol to the average received power spectral density of the total noise and interference for this RE, where the ratio is measured over all REs carrying PRS. Time T, as illustrated in the following figures_RSTDStarting from the first subframe of the temporally closest PRS positioning occasion after the OTDOA assistance data is delivered to the physical layer of the UE in an OTDOA-ProvideAssistanceData message specified in 3GPP TS 36.355.

The RSTD measurement accuracy of the neighbor cell i for all measurements should be met according to the accuracy requirement.

FIG. 7

Fig. 7 illustrates the RSTD reporting time requirement in FDD mode.

As shown in fig. 7, the measurement report is not delayed on the DCCH by other LPP signaling. This measurement report delay removes (include) the delay uncertainty that arises when the measurement report is inserted into the TTI of the uplink DCCH. The delay uncertainty is: 2 × TTIDCCH. This measurement report delay removes any delay caused by no UL resources for the UE to send a measurement report.

Table 5 shows the Reference Signal Time Difference (RSTD).

TABLE 5

[ Table 5]

Table 6 shows the accuracy required for RSTD measurement performed by the UE according to the bandwidth allocated for PRS by the neighbor cell. In table 6 this accuracy is valid under the following conditions:

the conditions for the reference sensitivity defined in section 36.101, 7.3 are met.

For bands 1, 4, 6, 10, 11, 18, 19, 21, 33, 34, 35, 36, 37, 38, 39, 40, PRP l,2| dBm ≧ 127dBm

For band 9, PRP l,2| dBm ≧ 126dBm

For bands 2, 5, 7, PRP l,2| dBm ≧ 125dBm

For bands 3, 8, 12, 13, 14, 17, 20, PRP l,2| dBm ≧ 124 dBm.

There are no measurement gaps that overlap with the PRS subframes of the measurement cell.

The signaled parameter expectedRSTDUnsequentialnity over LPP by E-SMLC is less than 5 mus as defined in 3GPP TS 36.355.

TABLE 6

[ Table 6]

Table 7 shows the relationship between the bandwidth and the number of Resource Blocks (RBs).

TABLE 7

[ Table 7]

Bandwidth [ MHz ]]	1.4	3	5	10	15	20
							RB	6	15	25	50	75	100

FIG. 8

Fig. 8 illustrates one example of a case where a bandwidth allocated by a serving cell is different from a bandwidth allocated by at least one or more neighbor cells.

Referring to fig. 8(a), if a UE belonging to a serving cell to which a bandwidth of 3MHz has been allocated tries to receive PRS from a target cell to which a bandwidth of 10MHz has been allocated for PRS, the accuracy of measurement is changed from ± 15Ts to ± 5 Ts. In other words, the accuracy is very strict.

Referring to fig. 8(b), if a bandwidth allocated for PRS by a serving cell is greater than a bandwidth allocated for PRS by a neighbor cell, when a UE tries to receive PRS from the neighbor cell, the UE may receive undesired interference via the bandwidth of the serving cell that is greater than the bandwidth of the neighbor cell. Such interference sometimes results in degraded accuracy.

Accordingly, a technique that satisfies the accuracy requirements for measuring the RTSD between neighboring cells having an intra-frequency based relationship will be described hereinafter.

Fig. 9 to 11 illustrate three embodiments of the present invention to improve accuracy.

FIG. 9

Fig. 9 illustrates a first embodiment of the present invention, in which PRS is measured considering the longest BW in the serving cell and the neighbor cells.

Referring to fig. 9, if a bandwidth allocated for PRS by a neighbor cell is greater than a bandwidth allocated for PRS by a serving cell, a first embodiment allows a UE to measure a Reference Signal Time Difference (RSTD) by using information on a bandwidth allocated for PRS by at least one neighbor cell.

In general, the accuracy of the measurement depends on the bandwidth allocated for the PRS to vary. And, the larger the bandwidth allocated for PRS, the higher the frequency sampling rate, thereby obtaining excellent measurement accuracy.

The UE may obtain information on a bandwidth allocated for the PRS by at least one neighbor cell by receiving the RRC signal message. Accordingly, the UE may select at least one cell having the largest bandwidth among the at least one neighbor cell and the serving cell. And, the UE considers the selected cell as a reference cell. And, the UE sets at least one parameter for measuring a timing difference between PRSs based on the maximum bandwidth. The parameter includes at least one of a first parameter related to accuracy with respect to the measurement, and a second parameter related to the number of subframes available for the measurement. And then, the UE measures RSTD between PRSs transmitted from the serving cell and the neighbor cell according to the set parameters.

In other words, as shown in fig. 9, if the bandwidth of the serving cell is not the maximum, the UE does not consider the serving cell as the reference cell. Instead, as shown in fig. 9, the UE measures PRS according to the maximum bandwidth allocated for PRS to obtain excellent accuracy.

However, if the UE tries to receive PRS from the serving cell and the neighboring cells (which allocate a bandwidth smaller than the maximum bandwidth), the interfering signal may also be received by the UE. However, since the UE has already acquired information on the bandwidth allocated by each cell, the UE can minimize the interference signal by using a digital filter.

As described so far, the first embodiment can satisfy the requirement for the measurement accuracy.

FIG. 10 shows a schematic view of a

Fig. 10 illustrates a second embodiment of the invention in which the bandwidth of the first cell is adjusted to be equal to the bandwidth of the other cells.

Referring to fig. 10, the second embodiment allows the serving cell and the neighbor cell to allocate the same bandwidth for PRS. To this end, the serving cell may exchange information about the bandwidth allocated for the PRS with the neighbor cell. After receiving this information, each neighboring cell adjusts the bandwidth allocation.

In more detail, the serving cell and the neighboring cells exchange information via an X2 interface. Alternatively, the operator may request the serving cell and the neighbor cells to allocate the same bandwidth by using an operation management (O & M) protocol.

FIGS. 11 and 12

Fig. 11 illustrates a third embodiment of the present invention. Also, fig. 12 illustrates an example of a measurement gap according to a third embodiment of the present invention.

Referring to fig. 11, a third embodiment allows a UE to sequentially receive a plurality of PRSs.

In more detail, if the bandwidth allocated for PRSs received from one cell is smaller or larger than the bandwidth allocated by the serving cell, the UE must tune the RF component in order to receive the corresponding PRSs in each bandwidth. However, such tuning requires time. Thus, the serving cell provides a time gap to the UE so that the UE has sufficient time to tune its RF components. For this reason, the serving cell cannot transmit any signal when the UE must receive a corresponding PRS from each neighboring cell.

To this end, the UE transmits a request message for requesting a gap to the serving cell. The request message includes information on a bandwidth allocated by at least one neighbor cell.

Meanwhile, the UE adaptively or actively controls its filter in order to receive PRSs in a corresponding bandwidth allocated by each cell, so that the UE can measure RSTDs between PRSs having an intra-frequency based relationship.

Table 7 shows the gap pattern used for the measurements. This gap is also used to monitor inter-frequency EARFCN and inter-RAT systems. The gap supports 40ms and 80 ms. Further, the measurement period may be 6 ms.

TABLE 8

[ Table 8]

In fact, in order to measure RSTD between PRSs, it is required to set a measurement gap in the physical layer. And, if the measurement gap is set, the measurement is performed in an optimal manner. Referring to fig. 12, there is a measurement gap between subframes in which a serving cell must transmit data.

FIGS. 13 and 14

Fig. 13 illustrates a case where the serving cell is not defined as the reference cell and the bandwidth allocated by the serving cell is greater than the bandwidth allocated by the target cell. Also, fig. 14 illustrates a problem and a solution that occur in a case where the serving cell is not defined as the reference cell and the bandwidth allocated by the serving cell is smaller than the bandwidth allocated by the target cell according to the fourth embodiment.

Referring to fig. 13, a serving cell allocates a 5MHz bandwidth for PRS, and a neighbor cell defined as a reference cell allocates a 15MHz bandwidth and a target cell also allocates a 3MHz bandwidth. Here, referring to table 7, 3MHz corresponds to 15 RBs, 5MHz corresponds to 25 RBs, and 15MHz corresponds to 75 RBs. Further, referring to table 6, if the bandwidth is 15 RBs, the number of subframes required for measurement is 6. And, if the bandwidth is 25 RBs, the number of subframes is 2. And further, if the bandwidth is 75 RBs, the number of subframes is 1.

Accordingly, PRS transmitted from a serving cell are measured during 2 subframes (or 2 TTIs). And, PRS transmitted from the reference cell is measured during 1 subframe. And, the PRS transmitted from the target cell is measured during 1 subframe.

Meanwhile, if the UE uses a filter to tune to a 5MHz bandwidth of the serving cell, the number of subframes is determined based on a smaller one among the bandwidth of the target cell and the bandwidth of the reference cell (in other words, the UE selects 6 subframes), and RSTD between PRSs transmitted from the serving cell and the target cell is measured with reference to the PRSs transmitted from the reference cell during the determined number of subframes, since measurement is performed during 6 subframes, which is a time long enough to receive the PRSs transmitted from the serving cell, and since the filter is tuned for 5MHz greater than 3MHz of the target cell, there is no problem.

However, referring to fig. 14(a), the serving cell is not defined as the reference cell, and the bandwidth allocated by the serving cell is smaller than the bandwidth allocated by the target cell.

In such a case, if the UE tunes to the 3MHz bandwidth of the serving cell using the filter, the RSTD between PRSs transmitted from the serving cell and the target cell is measured based on the number of selection subframes which is smaller among the bandwidth of the reference cell and the bandwidth of the target cell (in other words, the UE selects 2 subframes) and based on the PRS transmitted from the reference cell during the determined number of subframes, there is a problem in that the measurement performed during only 2 subframes is insufficient to satisfy the accuracy under the condition that the filter tunes to 3MHz which is smaller than 5MHz of the target cell. In other words, since the PRS on 5MHz transmitted from the target cell passes through a filter tuned for 3MHz, the initial 2 subframes are not sufficient.

To solve this problem, fig. 14(b) shows a solution according to the fourth embodiment. The fourth embodiment allows the UE to determine the number of subframes based on the smallest bandwidth among all cells including the serving cell, the reference cell, and the target cell.

In more detail, fig. 14(b) shows an example scenario in which the serving cell allocates 3MHz bandwidth for PRS and the target cell allocates 5MHz bandwidth.

In such a case, if the UE tunes to the 3MHz bandwidth of the serving cell using the filter, determines the number of subframes based on the smallest bandwidth among all cells including the serving cell, the reference cell, and the target cell (in other words, the UE selects 6 subframes), and measures the RSTD between the PRSs transmitted from the serving cell and the target cell based on the PRS transmitted from the reference cell during the determined number of subframes (i.e., during 6 subframes), there is no problem because the measurement is performed during 6 subframes, which is long enough to receive the PRS transmitted from the target cell, although the filter tunes to 3MHz, which is less than 5MHz of the target cell.

Meanwhile, according to the fourth embodiment, the UE transmits information on a parameter related to the determined number of subframes to the serving cell.

The method according to the present invention as described above may be implemented by software, hardware, or a combination of both. For example, the method according to the present invention may be stored in a storage medium (e.g., an internal memory, a flash memory, a hard disk, etc.) and may be implemented in a software program capable of being executed by a processor, such as a microprocessor, a controller, a microcontroller, an ASIC (application specific integrated circuit, etc.), via codes or instructions, hereinafter, it will be described with reference to FIG. 11.

FIG. 15 shows a schematic view of a

As illustrated in fig. 15, the UE 100 may include a storage unit 101, a transceiver 103, and a controller 102. Further, the base station 200 may include a storage unit 201, a transceiver 203, and a controller 202. The base station 200 may be a serving cell, a reference cell, or a target cell.

The storage unit stores a software program implementing the aforementioned method as illustrated in fig. 1 to 14. Further, the storage unit stores information within each of the received messages (or signals).

Each of the controllers controls the storage unit and the transceiver separately. In particular, the controller implements the aforementioned method stored separately in each of the storage units.

The invention has been explained with reference to only exemplary embodiments. It will be apparent to those skilled in the art that various modifications and equivalent other embodiments of the invention can be made without departing from the spirit or scope of the invention. Further, it is to be understood that the present invention can be implemented by selectively combining the aforementioned embodiments in whole or in part. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

1. A method for performing reference signal time difference, RSTD, measurements by a user equipment, UE, comprising:

receiving, by the UE, a Positioning Reference Signal (PRS) of a serving cell, a PRS of a neighbor cell, and a PRS of a reference cell; and

measuring, by the UE, RSTD based on the PRS, the PRS for RSTD measurement accuracy,

wherein the RSTD measurement accuracy is determined based on a minimum bandwidth which is a minimum of a bandwidth of the serving cell, a bandwidth of the neighbor cell, and a bandwidth of the reference cell, and

wherein a bandwidth of the serving cell, a bandwidth of the neighbor cell, and a bandwidth of the reference cell are related to the PRS.

2. The method of claim 1, further comprising:

receiving information on a bandwidth of a PRS for the neighbor cell and information on a bandwidth of a PRS for the reference cell.

3. The method of claim 1, further comprising:

receiving information on a number of consecutive downlink subframes having PRS of the neighbor cell and information on a number of consecutive downlink subframes having PRS of the reference cell.

4. The method according to any one of claims 1 to 3,

wherein the RSTD is measured in a certain number of downlink subframes, and

wherein the RSTD measurement accuracy relates to the number of downlink subframes during which the RSTD is measured.

5. The method according to any one of claims 1 to 3,

wherein the reference cell is different from the serving cell.

6. The method of any of claims 1 to 3, further comprising:

reporting, by the UE, the RSTD to a network for positioning of the UE.

7. A user equipment, UE, for performing reference signal time difference, RSTD, measurements, comprising:

a transceiver, and

a controller configured to control the transceiver, configured to:

control the transceiver to receive a positioning reference signal, PRS, of a serving cell, PRS of a neighbor cell, and PRS of a reference cell; and is

Measuring RSTD based on the PRS, the PRS being used for RSTD measurement accuracy,

8. The UE of claim 7, wherein the UE is further configured to,

wherein the transceiver further receives information on a bandwidth of a PRS for the neighbor cell and information on a bandwidth of a PRS for the reference cell.

9. The UE of claim 7, wherein the UE is further configured to,

wherein the transceiver further receives information on the number of consecutive downlink subframes having PRS of the neighbor cell and information on the number of consecutive downlink subframes having PRS of the reference cell.

10. The UE of claim 7, wherein the UE is further configured to,

wherein the controller is configured to measure the RSTD in a number of downlink subframes, and

11. The UE of claim 7, wherein the UE is further configured to,

wherein the reference cell is different from the serving cell.

12. The UE of claim 7, wherein the UE is further configured to,

wherein the controller is configured to control the transceiver to report the RSTD to a network for positioning of the UE.